Why would you think this stuff wasn't in writing? Do you think the investigation OAI did into the board's actions was just relayed orally?[1] That the board's discussions where all done in conference calls and not in e-mail? Do you think that this documentation gets routinely released to the public or even employees? Before you throw around accusations of incompetence, you should probably have some shred of evidence. This is the type of stuff that is typically considered extremely confidential and even now they say they are unable to reveal details. Why do you think that is? What is preventing them from doing something they apparently want to? Legal agreements such as NDAs, the same ones that would have prevented them from going public with details last years.
The board's mistake was not figuring out a way to go public with their case against Sam when or before they fired him. They obviously misjudged how he would respond. But even there we don't know the full context and constraints they were under. Hopefully, one of them will answer that question of why they didn't at some point, but until we know more, we would be wise to reserve judgement.